 Objectives
 To
learn the structure of the cell
membrane
 To learn how structure and function of the
cell membrane are linked
 To learn about different forms of
transport across the cell wall.
 Cell
is bound by a fluid membrane
 It regulates movement of chemicals in
and out of the cell;
 It is involved in recognition and
identification
 It facilitates the function of the cell
 It protects the cell
 It keeps the cell together
 It interacts with the membranes of other
cells
 http://www.youtube.com/watch?v=owEg
qrq51zY
1
A phospholipid bilayer which allows
the passage of lipids across the
membrane
 2. Bilayer of phospholipid molecules with
water loving heads on the inner and
outer surface and water hating tails
pointing into the membrane.
 We describe our understanding of it as
the ‘Singer and Nicholson’ fluid mosaic
model.
 Included in the phospholipid bilayer
 Integral proteins (carrier proteins)
 Peripheral proteins
 Cholesterol
 Carbohydrate chains
 Glycolipids (lipids with attached
are:
carbohydrate chains)
 Glycoproteins (proteins with attached
carbohydrate chains)
 These inclusions can move around the fluid
phospholipid bilayer.
 Carbohydrate
chains
 Give the cell a sugar coat or glycocalyx
which protects the cell.
 These carbohydrate chains are unique to
individuals, tissue types and blood
groups.
 They are what our immune system uses to
recognise our cells and invading ones.
 Allows
rapid movement of carrier
proteins around;
 Gives flexibility to cells, so e.g. your
nerve cells don’t crack when you bend.
 Membrane proteins move freely.
 Has been demonstrated by merging
human and mouse cells. In 40 minutes
membrane proteins from two cells
completely mixed.
 Channel
proteins: allow molecules to
move across the membrane through a
channel;
 Carrier proteins: combine with chemicals
to transport them across the membrane;
 Cell recognition proteins are
glycoproteins which allow us to
recognise our own cells and invaders and
therefore facilitate an immune response.
 Receptor
proteins: Have a shape that
allows one type of molecule to bind to it.
 Once the molecule is bound to it, it
changes shape altering the properties of
the cell.
 E.g. insulin binding to liver cells causes
them to store sugar.
 Enzymatic proteins carry out metabolic
functions.
 1. make
a model of the plasma
membrane
 2. Explain how your model shows its
different parts and functions
 3. Marking rubric same as for cell model.
 Known
as cell transport covers the
movement of substances in and out of the
cell membrane.
 Will include both the different types of
transport
 And the structure and function of the cell
membrane
 E.g. H2O, CO2 and O2 in and out of the cell.
 What is diffusion?
 http://www.youtube.com/watch?v=H7QsDs
8ZRMI
 Across
the cell membrane it is helped by
protein
 http://www.youtube.com/watch?v=OV4PgZ
DRTQw
 This is called facilitated diffusion
 An idea of random particle movement:
http://ccl.northwestern.edu/netlogo/models/DLA
 1. It
happens because of the natural
movement of the particles of liquids and
gases;
 2. It does not need an organism to use
energy;
 3. It can only happen down a
concentration gradient from higher to
lower concentrations;
 4. Across cell membranes it is assisted by
carrier proteins.
 The
diffusion of water across a semipermeable membrane;
 http://www.youtube.com/watch?v=sdiJtDRJ
QEc
 Important in enabling plant cells to absorb
water to maintain their turgor pressure;
 Results in dilution of the solution
 Water moves from weak solutions where
there is lots of water to strong solutions
where there is less water.
 Does not require energy
 Does require semi-permeable membrane.
 Hypotonic
solution is weaker than the
solution in the cell;
 Isotonic solution is equal to that in the cell;
 Hypertonic solution is stronger than that in
the cell;
 Lysed means split
 Turgid means full and firm
 Flaccid means limp, droopy
 Plasmolysed means cell membrane and
contents have shrunk away from the cell
wall in plants.
This does not require energy
 All chemicals pass down a concentration
gradient.
 It is necessary for the transport of materials like
glucose and some amino acids across the cell
membrane because they are not lipid soluble;
 It uses carrier molecules which are proteins
crossing the cell membrane
 Each carrier molecule is specific to one
molecule to be transported


Open this simulation and try to
show what is happening in a cell in different osmotic conditions
http://phet.colorado.edu/en/simulation/membrane-channels
 This
does require energy
 http://www.youtube.com/watch?v=STzOi
RqzzL4
 To summarise both facilitated and active
transport.
 http://www.youtube.com/watch?v=1ZFq
OvxXg9M&NR=1
 endocytosis
& exocyctosis are ways to
transport large molecules across a
membrane
 In some cases, receptor sites on the surface
of the cell bond with the large molecule
 Endocytosis takes in material from the cell
by pockets or in-foldings of the cell
membrane itself
• this happens by phagocytosis (solids) & pinocytosis
(liquids)
 release
of large amounts of material from
the cell
• The membrane of the vacuole surrounding the
material joins with the cell membrane, forcing
the contents out of the cell.
 Large amounts of water may be removed from a cell
in this way.
 type
of endocytosis
 this means “eating cell”
 cytoplasm surrounds a particle & package it
within a food vacuole
 next, the cell engulfs it (surrounds it)
• Amoebas use this to take in their food
 this
uses A LOT of energy= form of active
transport
 http://www.youtube.com/watch?v=_AASYG
G7mrw&feature=related
 the
taking up liquid from a cell’s
surrounding environment
 tiny pockets form along the cell
membrane, fill with liquid, and pinch off
to form vacuoles within the cell
 vitamins, nutrients and hormones may be
absorbed into a cell using pinocytosis
 The
sodium potassium pump.
 http://www.youtube.com/watch?v=GTH
Wig1vOnY
 Watch the video and write your own
voice over. You may work in pairs. Submit
video with your voice over recorded.
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Describe the structure of the plasma membrane.
Say how its structure affects the transport of materials across it.
Think about how chemicals are imported and exported from the
cell.
Describe how the structure of the cell membrane allows other
functions.
You must also describe the types of transport and say which parts
of the cell membrane they use and how they actually occur. Give
examples of each.
¼ of a mark to be deducted for each mistake spelling technical
words up to 2 marks
½ marks deducted for each time sentences are not correctly
separated with punctuation or joined appropriately and
meaningfully – up to 2 marks.
All information must be referenced. You may quote sections of
articles but must show this with quotation marks and you must
reference the information in the text. Minimum length 1000 words.
You must include labeled diagrams (2 marks). Content 14 marks
(total 20marks)